The warm air from the tropics contributed to the 2015-2016 summer being warmer than average for most of New Zealand.
Across most of the country, above average (+0.51°C to +1.20°C of the summer average) or well above average (> +1.20°C of the summer average) temperatures were experienced.
The North Island was particularly warm. The only locations in New Zealand where near average (-0.51°C to +0.50°C of the summer average) temperatures were recorded were in parts of coastal Canterbury. In particular, February was a notably warm month, with the second-highest national mean monthly temperature on record using NIWA’s seven-station temperature series. For the season as a whole, the nation-wide average temperature in summer 2015-16 was 17.5°C (0.9°C above the 1981-2010 summer average, using NIWA’s seven-station temperature series which begins in 1909).
The moist, humid tropical air masses affecting the country (including the remnants of four tropical cyclones) also caused numerous rain events throughout the summer. With its predominant south-westerly flow and high pressure over the country, December was a very dry month for many parts of New Zealand. But with the change to more northerly-quarter winds than usual for January and February which brought more rain, fears of El Niño-associated drought were alleviated in many parts of the country. For summer as a whole, near normal rainfall (80-119% of the summer normal) was observed for most of the upper half of the North Island, as well as Gisborne and northern Hawke’s Bay. Above normal rainfall (120-149% of the summer normal) was also recorded at certain sites in Northland and Coromandel. However, it was still a dry summer for some, with below normal rainfall (50-79% of the summer normal) for most of the lower half of the North Island. For the South Island, near normal rainfall was experienced in most places with pockets of above normal rainfall in West Coast, Tasman and Christchurch, and pockets of below normal rainfall (50-79% of the summer normal) in Marlborough, Queenstown-Lakes, and Central Otago.
Due to the heavy rainfall events that occurred in January and February, the patterns of soil moisture changed drastically throughout summer. At the end of December, soil moisture levels were below normal for the time of year for almost the entire country. However this changed overnight with heavy rain and flooding on New Year’s Day in northern parts of the country. As such, by the end of January soil moisture levels had increased somewhat over most of the country, particularly in areas such as Northland and Coromandel which were affected by rainfall over the New Year period. As of 1 March 2016, soil moisture levels were above normal for the time of year for eastern Northland and Auckland, Coromandel, the Bay of Plenty, northern Tasman, Nelson and parts of eastern Waikato and Southland. Drier than normal soils were evident in the remainder of the North Island as well as eastern parts of Canterbury and Otago.
Summer sunshine was relatively evenly distributed between above normal (110-125% of the summer normal) and near normal (90-109% of the summer normal) for different sites around the country (no distinct patterns observed), except for the Bay of Plenty which had below normal sunshine (75-89%). In fact, Tauranga had its cloudiest summer on record, with 77% of normal summer sunshine. The only location with well above normal sunshine (>125% of the summer normal) was Dunedin.
Further Highlights include:
- The highest temperature was 36.4°C, observed at Leeston on 21 December.
- The lowest temperature was -1.2°C, observed at Manapouri on 4 January.
- The highest 1-day rainfall was 331 mm, recorded at North Egmont 17 February.
- The highest wind gust was 183km/hr, observed at Cape Turnagain on 10 January.
- Of the six main centres in summer 2015-16, Auckland was the warmest, Dunedin was the coolest, Wellington was the driest and sunniest, and Tauranga was the wettest and cloudiest.
For further information, please contact:
Mr Chris Brandolino
NIWA Forecaster – NIWA National Climate Centre
Tel. (09) 375 6335, Mobile (027) 866 0014